Electronics systems, such as communication systems, radar systems, infrared-sensor systems, laser-tracking systems, or directed-energy systems, whether ground-based, mobile, airborne, shipboard, or spacecraft based, generally have several subsystems that receive power from a power source over an electric-power bus. Certain subsystems may draw a ripple current from the power source that may affect the other subsystems. Several specifications, such as MIL-STD-461, address the quantity and frequency content of ripple current that may be reflected to an electric-power bus, in addition to other requirements.
For example, in the case of certain types of sensor systems, a cryogenic cooler drive electronics system may draw up to 8 to 10 amps or more of ripple current at a nominal frequency between 35 and 100 Hz from the electric-power bus. In some applications, such as a satellite system, a large ripple-current draw may destabilize the bus and may degrade the performance of other electronics subsystems using the bus, particularly, those managing low power sensor signals. For example, in the case of a laser system that generates pulsed output energy, or a directed-energy system that generates pulses of RF energy, the current required for the pulsed output may similarly reflect back to an electric-power bus and may destabilize it.
Conventional approaches to reduce the current ripple on an electric-power bus utilize passive filters with large capacitors and inductors. However, the size and weight of these large capacitors and inductors required for low-frequency filter bandwidth make these approaches undesirable for applications where size and/or weight are important factors. Other conventional approaches include the use of shunt regulators in parallel with the load. These shunt regulators draw load current under light load conditions and reduce shunt power under system heavy load conditions keeping the net current draw from a power source somewhat constant. Although this approach may work well for relatively light fluctuating loads, it wastes power. At high power or for a large quantity of shunt regulators, the power dissipation of the shunt loads may become excessive increasing net total power draw and reducing the efficiency of the power system. AC-coupled shunt regulators are also used in conventional systems but also suffer from excessive power dissipation, and because they are AC coupled, they suffer from bandwidth limitations.
Thus, there are general needs to reduce ripple-current reflections to an electric-power bus. There are also general needs for systems and methods that control and regulate input current drawn from an electric-power bus. There are also needs for systems and methods that control and regulate input current drawn from an electric-power bus without the use of large capacitors, large inductors or shunt regulators. There are also needs for systems and methods that control and regulate input current drawn from an electric-power bus suitable for electronics systems, including ground-based, mobile, airborne, shipboard, and spacecraft-based systems.